Tectorigenin Attenuates Palmitate-Induced Endothelial Insulin Resistance via Targeting ROS-Associated Inflammation and IRS-1 Pathway

Endoplasmic reticulum stress in pancreatic β-cell dysfunction: The potential therapeutic role of dietary flavonoids

Diabetes mellitus (DM) is a global health burden that is characterized by the loss or dysfunction of pancreatic β-cells. In pancreatic β-cells, endoplasmic reticulum (ER) stress is a fact of life that contributes to β-cell loss or dysfunction. Despite recent advances in research, the existing treatment approaches such as lifestyle modification and use of conventional therapeutics could not prevent the loss or dysfunction of pancreatic β-cells to abrogate the disease progression. Therefore, targeting ER stress and the consequent unfolded protein response (UPR) in pancreatic β-cells may be a potential therapeutic strategy for diabetes treatment. Dietary phytochemicals have therapeutic applications in human health owing to their broad spectrum of biochemical and pharmacological activities. Flavonoids, which are commonly obtained from fruits and vegetables worldwide, have shown promising prospects in alleviating ER stress. Dietary flavonoids including quercetin, kaempferol, myricetin, isorhamnetin, fisetin, icariin, apigenin, apigetrin, vitexin, baicalein, baicalin, nobiletin hesperidin, naringenin, epigallocatechin 3-O-gallate hesperidin (EGCG), tectorigenin, liquiritigenin, and acacetin have shown inhibitory effects on ER stress in pancreatic β-cells. Dietary flavonoids modulate ER stress signaling components, chaperone proteins, transcription factors, oxidative stress, autophagy, apoptosis, and inflammatory responses to exert their pharmacological effects on pancreatic β-cells ER stress. This review focuses on the role of dietary flavonoids as potential therapeutic adjuvants in preserving pancreatic β-cells from ER stress. Highlights of the underlying mechanisms of action are also presented as well as possible strategies for clinical translation in the management of DM.

Tectorigenin: A Review of Its Sources, Pharmacology, Toxicity, and Pharmacokinetics

Tectorigenin is a well-known natural flavonoid aglycone and an active component that exists in numerous plants. Growing evidence suggests that tectorigenin has multiple pharmacological effects, such as anticancer, antidiabetic, hepatoprotective, anti-inflammatory, antioxidative, antimicrobial, cardioprotective, and neuroprotective. These pharmacological properties provide the basis for the treatment of many kinds of illnesses, including several types of cancer, diabetes, hepatic fibrosis, osteoarthritis, Alzheimer's disease, etc. The purpose of this paper is to provide a comprehensive summary and review of the sources, extraction and synthesis, pharmacological effects, toxicity, pharmacokinetics, and delivery strategy aspects of tectorigenin. Tectorigenin may exert certain cytotoxicity, which is related to the administration time and concentration. Pharmacokinetic studies have demonstrated that the main metabolic pathways in rats for tectorigenin are glucuronidation, sulfation, demethylation and methoxylation, but that it exhibits poor bioavailability. From our perspective, further research on tectorigenin should cover: exploring the pharmacological targets and mechanisms of action; finding an appropriate concentration to balance pharmacological effects and toxicity; attempting diversified delivery strategies to improve the bioavailability; and structural modification to obtain tectorigenin derivatives with higher pharmacological activity.

Anti-Glucotoxicity Effect of Phytoconstituents via Inhibiting MGO-AGEs Formation and Breaking MGO-AGEs

The therapeutic benefits of phytochemicals in the treatment of various illnesses and disorders are well documented. They show significant promise for the discovery and creation of novel medications for treating a variety of human diseases. Numerous phytoconstituents have shown antibiotic, antioxidant, and wound-healing effects in the conventional system. Traditional medicines based on alkaloids, phenolics, tannins, saponins, terpenes, steroids, flavonoids, glycosides, and phytosterols have been in use for a long time and are crucial as alternative treatments. These phytochemical elements are crucial for scavenging free radicals, capturing reactive carbonyl species, changing protein glycation sites, inactivating carbohydrate hydrolases, fighting pathological conditions, and accelerating the healing of wounds. In this review, 221 research papers have been reviewed. This research sought to provide an update on the types and methods of formation of methylglyoxal-advanced glycation end products (MGO-AGEs) and molecular pathways induced by AGEs during the progression of the chronic complications of diabetes and associated diseases as well as to discuss the role of phytoconstituents in MGO scavenging and AGEs breaking. The development and commercialization of functional foods using these natural compounds can provide potential health benefits.

Impairment of insulin signaling pathway PI3K/Akt/mTOR and insulin resistance induced AGEs on diabetes mellitus and neurodegenerative diseases: a perspective review

Insulin resistance is common in type 2 diabetes mellitus (T2DM), neurodegenerative diseases, cardiovascular diseases, kidney diseases, and polycystic ovary syndrome. Impairment in insulin signaling pathways, such as the PI3K/Akt/mTOR pathway, would lead to insulin resistance. It might induce the synthesis and deposition of advanced glycation end products (AGEs), reactive oxygen species, and reactive nitrogen species, resulting in stress, protein misfolding, protein accumulation, mitochondrial dysfunction, reticulum function, and metabolic syndrome dysregulation, inflammation, and apoptosis. It plays a huge role in various neurodegenerative diseases like Parkinson's disease, Alzheimer's disease, Huntington's disease, and Amyloid lateral sclerosis. In this review, we intend to focus on the possible effect of insulin resistance in the progression of neurodegeneration via the impaired P13K/Akt/mTOR signaling pathway, AGEs, and receptors for AGEs.

A pinitol-rich Glycyrrhiza glabra L. leaf extract as functional supplement with potential in the prevention of endothelial dysfunction through improving insulin signalling

Background: Glycyrrhyza glabra L. is one of the most popular medicinal plant in the world, its roots having been used since ancient times in many traditional medicines. On the contrary, scarce attention has been dedicated to liquorice aerial parts. Previous studies showed the presence of a large group of polyphenols and a consistent amount of d-pinitol in the leaf extract.Methods: The methanolic extract from G. glabra leaves was profiled for its content in polyphenols; the amount of d-pinitol was also measured with two independent methods (HPLC-ELSD and NMR). The extract was tested for its in vitro protective effects against insulin resistance-related endothelial dysfunction in human umbilical vein endothelial cells exposed to palmitic acid, which is the most prevalent saturated free fatty acid in circulation.Results: Methanolic extract from liquorice leaves has a protective effect against the lipotoxicity-associated alterations of insulin pathway in human endothelial cells, similarly to what observed with pure d-pinitol.Conclusions: Liquorice leaves are to be considered a waste product which gives a phytocomplex endowed with interesting potential therapeutic properties, moreover the use of a liquorice leaves phytocomplex rather than a pure compound allows avoiding a series of isolation/purification procedures and can be easily scaled up for industrial applications.

The monomer TEC of blueberry improves NASH by augmenting tRF-47-mediated autophagy/pyroptosis signaling pathway

Background

Nonalcoholic steatohepatitis (NASH) is one of the most common liver diseases and has no safe and effective drug for treatment. We have previously reported the function of blueberry, but the effective monomer and related molecular mechanism remain unclear.

Methods

The monomer of blueberry was examined by ultra performance liquid chromatography-mass spectrometry (UPLC-MS). The NASH cell model was constructed by exposing HepG2 cells to free fatty acids. The NASH mouse model was induced by a high-fat diet for 12 weeks. NASH cell and mouse models were treated with different concentrations of blueberry monomers. The molecular mechanism was studied by Oil Red O staining, ELISA, enzyme activity, haematoxylin–eosin (H&E) staining, immunohistochemistry, immunofluorescence, western blot, RNA sequencing, and qRT-PCR.

Results

We identified one of the main monomer of blueberry as tectorigenin (TEC). Cyanidin-3-O glucoside (C3G) and TEC could significantly inhibit the formation of lipid droplets in steatosis hepatocytes, and the effect of TEC on the formation of lipid droplets was significantly higher than that of C3G. TEC can promote cell proliferation and inhibit the release of inflammatory mediators in NASH cell model. Additionally, TEC administration provided a protective role against high-fat diets induced lipid damage, and suppressed lipid accumulation. In NASH mouse model, TEC can activate autophagy, inhibit pyroptosis and the release of inflammatory mediators. In NASH cell model, TEC inhibited pyroptosis by stimulating autophagy. Then, small RNA sequencing revealed that TEC up-regulated the expression of tRF-47-58ZZJQJYSWRYVMMV5BO (tRF-47). The knockdown of tRF-47 blunted the beneficial effects of TEC on NASH in vitro, including inhibition of autophagy, activation of pyroptosis and release of inflammatory factors. Similarly, suppression of tRF-47 promoted the lipid injury and lipid deposition in vivo.

Conclusions

These results demonstrated that tRF-47-mediated autophagy and pyroptosis plays a vital role in the function of TEC to treat NASH, suggesting that TEC may be a promising drug for the treatment of NASH.

Tectorigenin attenuates the OGD/R-induced HT-22 cell damage through regulation of the PI3K/AKT and the PPARγ/NF-κB pathways

Tectorigenin (TEC) is an effective compound that derived from many plants, such as Iris unguicularis, Belamcanda chinensis and Pueraria thunbergiana Benth. Evidence suggested that TEC has anti-tumor, anti-oxidant activity, anti-bacterial and anti-inflammatory effects. In addition, there has some evidence indicated that TEC is a potential anti-stroke compound; however, its specific roles and associated mechanism have not yet been elucidated. In the present study, we aimed to investigate the anti-inflammatory, anti-oxidant activity and anti-apoptosis effects of TEC on oxygen-glucose deprivation/reperfusion (OGD/R)-induced HT-22 cells, and clarified the relevant mechanisms. Here, we observed that TEC significantly promoted cell survival, impeded cell apoptosis, inhibited ROS and inflammatory cytokines IL-1β, IL-6, TNF-α production in OGD/R-induced HT-22 cells. Moreover, TEC activated PI3K/AKT signal pathway, increased PPARγ expression and inhibited NF-κB pathway activation in OGD/R-induced HT-22 cells. Further studies indicated that PPARγ inhibitor GW9662 activated NF-κB pathway after TEC treatment in OGD/R-induced HT-22 cells. Also, PI3K/AKT inhibitor LY294002, PPARγ inhibitor GW9662 and NF-κB activator LPS both reversed the effects of TEC on OGD/R-induced HT-22 cell biology. Taken together, this research confirmed that TEC benefit to HT-22 cell survival and against OGD/R damage through the PI3K/AKT and PPARγ/NF-κB pathways. These results indicated that TEC might be an effective compound in the treatment for ischemic brain injury.

Iris domestica (iso)flavone 7- and 3'-O-Glycosyltransferases Can Be Induced by CuCl2

In many plants, isoflavones are the main secondary metabolites that have various pharmacological activities, but the low water solubility of aglycones limits their usage. The O-glycosylation of (iso)flavones is a promising way to overcome this barrier. O-glycosyltransferases (UGTs) are key enzymes in the biosynthesis of (iso)flavonoid O-glycosides in plants. However, limited investigations on isoflavonoid O-UGTs have been reported, and they mainly focused on legumes. Iris domestica (L.) Goldblatt et Mabberley is a non-legume plant rich in various isoflavonoid glycosides. However, there are no reports regarding its glycosylation mechanism, despite the I. domestica transcriptome previously being annotated as having non-active isoflavone 7-O-UGTs. Our previous experiments indicated that isoflavonoid glycosides were induced by CuCl₂ in I. domestica calli; therefore, we hypothesized that isoflavone O-UGTs may be induced by Cu²⁺. Thus, a comparative transcriptome analysis was performed using I. domestica seedlings treated with CuCl₂, and eight new active BcUGTs were obtained. Biochemical analyses showed that most of the active BcUGTs had broad substrate spectra; however, substrates lacking 5-OH were rarely catalyzed. Real-time quantitative PCR results further indicated that the transcriptional levels of BcUGTs were remarkably induced by Cu²⁺. Our study increases the understanding of UGTs and isoflavone biosynthesis in non-legume plants.

Tectorigenin Alleviates Inflammation, Apoptosis, and Ossification in Rat Tendon-Derived Stem Cells via Modulating NF-Kappa B and MAPK Pathways

Tendinopathy is a common musculoskeletal disorder that mainly affects athletes and people of older age. Tumor necrosis factor-α (TNF-α) plays an important role in initiating tendinopathy. Tectorigenin, an extract component of Belam-canda Chinesis, possesses anti-inflammatory and anti-apoptosis activity. The present study was established to investigate the role of tectorigenin against the pathogenetic effects of TNF-α on tendon-derived stem cells (TDSCs) in vivo and in vitro. The findings indicated that TNF-α is able to induce TDSC inflammation, apoptosis, and ossification, as well as activate nuclear factor-kappa B and mitogen-activated protein kinase (MAPK). Furthermore, the results confirmed that tectorigenin is able to inhibit the TNF-α-induced inflammation, apoptosis, and ossification. Tectorigenin treatment decreases activation of NF-kappa B and MAPK signaling in TDSCs. Tectorigenin ameliorates tendinopathy in the in vivo rat model. Thus, these data reveal that tectorigenin can serve as a potential treatment for tendinopathy.

Tectorigenin enhances PDX1 expression and protects pancreatic β-cells by activating ERK and reducing ER stress

Pancreas/duodenum homeobox protein 1 (PDX1) is an important transcription factor that regulates islet β-cell proliferation, differentiation, and function. Reduced expression of PDX1 is thought to contribute to β-cell loss and dysfunction in diabetes. Thus, promoting PDX1 expression can be an effective strategy to preserve β-cell mass and function. Previously, we established a PDX1 promoter-dependent luciferase system to screen agents that can promote PDX1 expression. Natural compound tectorigenin (TG) was identified as a promising candidate that could enhance the activity of the promoter for the PDX1 gene. In this study, we first demonstrated that TG could promote the expression of PDX1 in β-cells via activating extracellular signal-related kinase (ERK), as indicated by increased phosphorylation of ERK; this effect was observed under either normal or glucotoxic/lipotoxic conditions. We then found that TG could suppress induced apoptosis and improved the viability of β-cells under glucotoxicity and lipotoxicity by activation of ERK and reduction of reactive oxygen species and endoplasmic reticulum (ER) stress. These effects held true in vivo as well: prophylactic or therapeutic use of TG could obviously inhibit ER stress and decrease islet β-cell apoptosis in the pancreas of mice given a high-fat/high-sucrose diet (HFHSD), thus dramatically maintaining or restoring β-cell mass and islet size, respectively. Accordingly, both prophylactic and therapeutic use of TG improved HFHSD-impaired glucose metabolism in mice, as evidenced by ameliorating hyperglycemia and glucose intolerance. Taken together, TG, as an agent promoting PDX1 expression exhibits strong protective effects on islet β-cells both in vitro and in vivo.

Investigation of effect of tectorigenin (O-methylated isoflavone) on Ca2+ signal transduction and cytotoxic responses in canine renal tubular cells

Tectorigenin, a traditional Chinese medicine, is isolated from the flower of plants such as Pueraria thomsonii Benth. It is an O-methylated isoflavone, a type of flavonoid. Previous studies have shown that tectorigenin evoked various physiological responses in different models, but the effect of tectorigenin on cytosolic-free Ca²⁺ levels ([Ca²⁺]_i) and cytotoxicity in renal tubular cells is unknown. Our research explored if tectorigenin changed Ca²⁺ signal transduction and viability in Madin-Darby Canine Kidney (MDCK) renal tubular cells. [Ca²⁺]_iin suspended cells were measured by applying the fluorescent Ca²⁺-sensitive probe fura-2. Viability was explored by using water-soluble tetrazolium-1 as a fluorescent dye. Tectorigenin at concentrations of 5-50 μM induced [Ca²⁺]_irises. Ca²⁺ removal reduced the signal by approximately 20%. Tectorigenin (50 μM) induced Mn²⁺ influx suggesting of Ca²⁺ entry. Tectorigenin-induced Ca²⁺ entry was inhibited by 10% by three inhibitors of store-operated Ca²⁺ channels, namely, nifedipine, econazole, and SKF96365. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin inhibited 83% of tectorigenin-evoked [Ca²⁺]_irises. Conversely, treatment with tectorigenin abolished thapsigargin-evoked [Ca²⁺]_irises. Inhibition of phospholipase C with U73122 inhibited 50% of tectorigenin-induced [Ca²⁺]_irises. Tectorigenin at concentrations between 10 and 60 μM killed cells in a concentration-dependent fashion. Chelation of cytosolic Ca²⁺ with 1,2-bis (2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid/acetoxy methyl did not reverse tectorigenin's cytotoxicity. Our data suggest that, in MDCK cells, tectorigenin evoked [Ca²⁺]_irises and induced cell death that was not associated with [Ca²⁺]_irises. Therefore, tectorigenin may be a Ca²⁺-independent cytotoxic agent for kidney cells.

Comprehensive transcriptome analysis reveals genes potentially involved in isoflavone biosynthesis in Pueraria thomsonii Benth

Pueraria thomsonii Benth is an important medicinal plant. Transcriptome sequencing, unigene assembly, the annotation of transcripts and the study of gene expression profiles play vital roles in gene function research. However, the full-length transcriptome of P. thomsonii remains unknown. Here, we obtained 44,339 nonredundant transcripts of P. thomsonii by using the PacBio RS II Isoform and Illumina sequencing platforms, of which 43,195 were annotated genes. Compared with the expression levels in the plant roots, those of transcripts with a |fold change| ≥ 4 and FDR < 0.01 in the leaves or stems were assigned as differentially expressed transcripts (DETs). In total, we found 9,225 DETs, 32 of which came from structural genes that were potentially involved in isoflavone biosynthesis. The expression profiles of 8 structural genes from the RNA-Seq data were validated by qRT-PCR. We identified 437 transcription factors (TFs) that were positively or negatively correlated with at least 1 of the structural genes involved in isoflavone biosynthesis using Pearson correlation coefficients (r) (r > 0.8 or r < -0.8). We also identified a total of 32 microRNAs (miRNAs), which targeted 805 transcripts. These miRNAs caused enriched function in ‘ATP binding’, ‘defense response’, ‘ADP binding’, and ‘signal transduction’. Interestingly, MIR156a potentially promoted isoflavone biosynthesis by repressing SBP, and MIR319 promoted isoflavone biosynthesis by repressing TCP and HB-HD-ZIP. Finally, we identified 2,690 alternative splicing events, including that of the structural genes of trans-cinnamate 4-monooxygenase and pullulanase, which are potentially involved in the biosynthesis of isoflavone and starch, respectively, and of three TFs potentially involved in isoflavone biosynthesis. Together, these results provide us with comprehensive insight into the gene expression and regulation of P. thomsonii.

Tectorigenin inhibits RANKL-induced osteoclastogenesis via suppression of NF-κB signalling and decreases bone loss in ovariectomized C57BL/6

Metabolism of bone is regulated by the balance between osteoblast‐mediated bone formation and osteoclast‐mediated bone resorption. Activation of osteoclasts could lead to osteoporosis. Thus, inhibiting the activity of osteoclasts becomes an available strategy for the treatment of osteoporosis. Tectorigenin is an extract of Belamcanda chinensis In the present study, the anti‐osteoclastogenesis effects of tectorigenin were investigated in vitro and in vivo. The results showed preventive and therapeutic effects of tectorigenin at concentrations of 0, 10, 40, and 80 μmol/L in the maturation and activation of osteoclasts. A signalling study also indicated that tectorigenin treatment reduces activation of NF‐κB signalling in osteoclastogenesis. Animal experiment demonstrated that tectorigenin treatment (1‐10 mg/kg, abdominal injection every 3 days) significantly inhibits bone loss in ovariectomized C57BL/6. Our data suggest that tectorigenin is a potential pharmacological choice for osteoporosis.

Cellular Stresses and Stress Responses in the Pathogenesis of Insulin Resistance

Insulin resistance (IR), a key component of the metabolic syndrome, precedes the development of diabetes, cardiovascular disease, and Alzheimer's disease. Its etiological pathways are not well defined, although many contributory mechanisms have been established. This article summarizes such mechanisms into the hypothesis that factors like nutrient overload, physical inactivity, hypoxia, psychological stress, and environmental pollutants induce a network of cellular stresses, stress responses, and stress response dysregulations that jointly inhibit insulin signaling in insulin target cells including endothelial cells, hepatocytes, myocytes, hypothalamic neurons, and adipocytes. The insulin resistance-inducing cellular stresses include oxidative, nitrosative, carbonyl/electrophilic, genotoxic, and endoplasmic reticulum stresses; the stress responses include the ubiquitin-proteasome pathway, the DNA damage response, the unfolded protein response, apoptosis, inflammasome activation, and pyroptosis, while the dysregulated responses include the heat shock response, autophagy, and nuclear factor erythroid-2-related factor 2 signaling. Insulin target cells also produce metabolites that exacerbate cellular stress generation both locally and systemically, partly through recruitment and activation of myeloid cells which sustain a state of chronic inflammation. Thus, insulin resistance may be prevented or attenuated by multiple approaches targeting the different cellular stresses and stress responses.

Comparison of Methods for Analyzing Human Adipose Tissue Macrophage Content

OBJECTIVE

The relationship between inflammation, obesity, and adverse metabolic conditions is associated with adipose tissue macrophages (ATM). This study compared the measurements of human ATM using flow cytometry, immunohistochemistry (IHC), and real-time polymerase chain reaction (RT-PCR) of ATM markers.

METHODS

A new software program (AMCounter) was evaluated to help measure ATM using IHC, and this was compared to flow cytometry and RT-PCR.

RESULTS

IHC had good intraindividual reproducibility for total (CD68), proinflammatory (CD14), and anti-inflammatory (CD206) ATM. The AMCounter improved interreader agreement and was more time efficient. Flow cytometry had acceptable intraindividual reproducibility for the percentage of CD68⁺ cells that were CD14⁺ or CD206⁺ , but not for ATMs per gram of tissue. ATMs per gram of tissue was much greater using IHC than flow cytometry. The flow cytometry and IHC measures of ATM from the same biopsies were not correlated. There were statistically significant correlations between RT-PCR CD68 and IHC CD68, CD14, and CD206 ATMs per 100 adipocytes. Also of interest were statistically significant correlations between RT-PCR CD68 and IHC CD68, CD14, and adipose flow cytometry measures of CD68⁺ , CD68⁺ /CD14⁺ , and CD68⁺ /CD206⁺ ATMs per gram of tissue.

CONCLUSIONS

The AMCounter software helps provide reproducible and efficient measures of IHC ATMs. Flow cytometry, IHC, and RT-PCR measures of adipose inflammation provide somewhat different information.

The Contribution of Singlet Oxygen to Insulin Resistance

Insulin resistance contributes to the development of diabetes and cardiovascular dysfunctions. Recent studies showed that elevated singlet oxygen-mediated lipid peroxidation precedes and predicts diet-induced insulin resistance (IR), and neutrophils were suggested to be responsible for such singlet oxygen production. This review highlights literature suggesting that insulin-responsive cells such as endothelial cells, hepatocytes, adipocytes, and myocytes also produce singlet oxygen, which contributes to insulin resistance, for example, by generating bioactive aldehydes, inducing endoplasmic reticulum (ER) stress, and modifying mitochondrial DNA. In these cells, nutrient overload leads to the activation of Toll-like receptor 4 and other receptors, leading to the production of both peroxynitrite and hydrogen peroxide, which react to produce singlet oxygen. Cytochrome P450 2E1 and cytochrome c also contribute to singlet oxygen formation in the ER and mitochondria, respectively. Endothelial cell-derived singlet oxygen is suggested to mediate the formation of oxidized low-density lipoprotein which perpetuates IR, partly through neutrophil recruitment to adipose tissue. New singlet oxygen-involving pathways for the formation of IR-inducing bioactive aldehydes such as 4-hydroperoxy-(or hydroxy or oxo)-2-nonenal, malondialdehyde, and cholesterol secosterol A are proposed. Strategies against IR should target the singlet oxygen-producing pathways, singlet oxygen quenching, and singlet oxygen-induced cellular responses.

Resveratrol Ameliorates Palmitate-Induced Inflammation in Skeletal Muscle Cells by Attenuating Oxidative Stress and JNK/NF-κB Pathway in a SIRT1-Independent Mechanism

Resveratrol has been shown to exert anti-inflammatory and anti-oxidant effects in a variety of cell types, however, its role in prevention of inflammatory responses mediated by palmitate in skeletal muscle cells remains unexplored. In the present study, we investigated the effects of resveratrol on palmitate-induced inflammation and elucidated the underlying mechanisms in skeletal muscle cells. The results showed that palmitate significantly enhanced TNF-α and IL-6 mRNA expression and protein secretion from C2C12 cells at 12, 24, and 36 h treatments. Increased expression of cytokines was accompanied by an enhanced phosphorylation of JNK, P38, ERK1/2, and IKKα/IKKβ. In addition, JNK and P38 inhibitors could significantly attenuate palmitate-induced mRNA expression of TNF-α and IL-6, respectively, whereas NF-κB inhibitor reduced the expression of both cytokines in palmitate-treated cells. Resveratrol pretreatment significantly prevented palmitate-induced TNF-α and IL-6 mRNA expression and protein secretion in C2C12 cells. Importantly, pre-treatment of the cells with resveratrol completely abrogated the phosphorylation of ERK1/2, JNK, and IKKα/IKKβ in palmitate treated cells. The protection from palmitate-induced inflammation by resveratrol was accompanied by a decrease in the generation of reactive oxygen species (ROS). N-acetyl cysteine (NAC), a known scavenger of ROS, could protect palmitate-induced expression of TNF-α and IL-6. Furthermore, inhibition of SIRT1 by shRNA or sirtinol demonstrated that the anti-inflammatory effect of resveratrol in muscle cells is mediated through a SIRT1-independent mechanism. Taken together, these findings suggest that resveratrol may represent a promising therapy for prevention of inflammation in skeletal muscle cells. J. Cell. Biochem. 118: 2654-2663, 2017. © 2017 Wiley Periodicals, Inc.

Watsonianone A from Rhodomyrtus tomentosa Fruit Attenuates Respiratory-Syncytial-Virus-Induced Inflammation In Vitro

Respiratory syncytial virus (RSV) is one of the most common respiratory pathogens. Immoderate inflammation plays a great role in causing RSV-induced diseases. In the present study, watsonianone A, isolated from the fruit of Rhodomyrtus tomentosa (Ait.) Hassk, was found to show a good inhibitory effect on RSV-induced NO production, with a half-maximal inhibitory concentration of 37.2 ± 1.6 μM. Enzyme-linked immunosorbent assay and fluorescence quantitative polymerase chain reaction analyses indicated that watsonianone A markedly reduced both mRNA and protein levels of tumor necrosis factor α, interleukin 6, and monocyte chemoattractant protein 1 in RSV-infected RAW264.7 cells. Mechanistically, watsonianone A inhibited nuclear factor κB (NF-κB) activation by suppressing IκBα phosphorylation. Further analysis revealed that watsonianone A activated the thioredoxin system and decreased intracellular reactive oxygen species (ROS) levels, which are closely associated with NF-κB activation in RSV-infected cells. These results reveal that watsonianone A can attenuate RSV-induced inflammation via the suppression of ROS-sensitive inflammatory signaling.

Timosaponin B-II Ameliorates Palmitate-Induced Insulin Resistance and Inflammation via IRS-1/PI3K/Akt and IKK/NF-[Formula: see text]B Pathways

This study aimed to investigate the effect of timosaponin B-II (TB-II) on palmitate (PA)-induced insulin resistance and inflammation in HepG2 cells, and probe the potential mechanisms. TB-II, a main ingredient of the traditional Chinese medicine Anemarrhena asphodeloides Bunge, notably ameliorated PA-induced insulin resistance and inflammation, and significantly improved cell viability, decreased PA-induced production of tumor necrosis factor-[Formula: see text] (TNF-[Formula: see text]) and interleukin-6 (IL-6) levels. Further, TB-II treatment notably decreased malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels, and improved superoxide dismutase (SOD) and nitric oxide (NO). TB-II also reduced HepG2 cells apoptosis. Insulin receptor substrate-1 (IRS1)/phosphatidylinositol 3-kinase (PI3K)/Akt and inhibitor of nuclear factor [Formula: see text]-B kinase (IKK)/NF-[Formula: see text]B pathways-related proteins, and IKK[Formula: see text], p65 phosphorylation, serine phosphorylation of insulin receptor substrate-1 (IRS-1) at S307, tyrosine phosphorylation of IRS-1, and Akt activation were determined by Western blot. Compared to model group, TB-II significantly downregulated the expression of p-NF-[Formula: see text]Bp65, p-IKK[Formula: see text], p-IRS-1, p-PI3K and p-Akt. TB-II is a promising potential agent for the management of palmitate-induced insulin resistance and inflammation, which might be via IR/IRS-1/PI3K/Akt and IKK/NF-[Formula: see text]B pathways.

Fucoidan from sea cucumber may improve hepatic inflammatory response and insulin resistance in mice

Nutrition excess-induced inflammation positively contributed to insulin resistance. Fucoidan from sea cucumber can increase glucose translocation in skeletal muscle. However, its effects on inflammation-associated insulin resistance are not understood. We investigated fucoidan from Isostichopus badionotus (Ib-FUC)-alleviated inflammatory response and signaling as well as -improved insulin resistance in the liver of obesity mice. The results showed that Ib-FUC reduced body weight and glucose levels, increased insulin sensitivity, and inhibited serum lipid concentrations. Meanwhile, Hepatic glycogen synthesis was promoted by Ib-FUC via activation of the PI3K/PKB/GSK-3β signaling and regulation of glucose metabolism-related enzymatic activities. Ib-FUC regulated serum inflammatory cytokines and their mRNA expression in the liver. Ib-FUC-induced inactivation of the JNK and IKKβ/NFκB pathways was involved in the activation of insulin signal cascade and inflammatory factor production. These findings suggested that Ib-FUC supplementary-induced alleviation of inflammatory response could be a mechanism responsible for its beneficial effects against hepatic insulin resistance.

Insights into the molecular mechanisms of diabetes-induced endothelial dysfunction: focus on oxidative stress and endothelial progenitor cells

Diabetes mellitus is a heterogeneous, multifactorial, chronic disease characterized by hyperglycemia owing to insulin insufficiency and insulin resistance (IR). Recent epidemiological studies showed that the diabetes epidemic affects 382 million people worldwide in 2013, and this figure is expected to be 600 million people by 2035. Diabetes is associated with microvascular and macrovascular complications resulting in accelerated endothelial dysfunction (ED), atherosclerosis, and cardiovascular disease (CVD). Unfortunately, the complex pathophysiology of diabetic cardiovascular damage is not fully understood. Therefore, there is a clear need to better understand the molecular pathophysiology of ED in diabetes, and consequently, better treatment options and novel efficacious therapies could be identified. In the light of recent extensive research, we re-investigate the association between diabetes-associated metabolic disturbances (IR, subclinical inflammation, dyslipidemia, hyperglycemia, dysregulated production of adipokines, defective incretin and gut hormones production/action, and oxidative stress) and ED, focusing on oxidative stress and endothelial progenitor cells (EPCs). In addition, we re-emphasize that oxidative stress is the final common pathway that transduces signals from other conditions-either directly or indirectly-leading to ED and CVD.